A new study on sugar gliders' genetics published on the 13th of july suggests that what was known as sugar glider is in fact 3 distinct species, and that the true sugar gliders are in fact a lot rarer than previously thought, which suggest that those held in captivity are likely not even sugar gliders (Petaurus breviceps) at all but most likely Krefft’s glider (Petaurus notatus) instead

https://www.australiangeographic.com.au/topics/wildlife/2020/07/meet-the-the-savanna-glider-scientists-have-discovered-sugar-glider-is-actually-three-species/?utm_source=website_cta&utm_medium=read-next&utm_campaign=on_site_links

I remember there always being more than just 3 species of sugar gliders. I think that article might only be referring to sugar gliders in Australia, and not necessarily world wide because there are also sugar gliders native to Indonesia as well.

There are a few members here, probably not active anymore, from Australia. Anecdotally, the gliders in the southern portion of Australia that they were from were noticeably larger than gliders seem in captivity in the United States.

Going on the size difference alone, one possibility is that the gliders in the US are most likely a species from Indonesia.

We were talking about subspecies , which are population groups inside a same species, not different species. (I know most people use the word species loosely, but in biology it has a specific meaning which is important in term both conservation and breeding)

The difference in size you mention is actually a known effect depending on latitude, the Bergmann's rule (members of a species have a higher body mass in higher latitude than their lower latitude counterparts).

The only case of "separate species" that had been mentionned so far was the caramel gliders, which have been supposed to be a different species alltogether leading to fertility issues on male opffsprings when crossed with regular gliders.

This study actually defines 3 totally genetically divergent (one of those is genetically closer to the mahogany glider than to the sugar glider), which also means that the sugar glider, and the 2 other species, are a lot rarer than previously thought, and are not so "least concern" in term of possible extinction (3 small population species instead of 1 big population and the risk on each population rise)